This invention relates to an internal combustion engine and more particularly to an improved spark plug mounting arrangement for the cylinder heads of such engine.
With many types of internal combustion engines and particularly those utilized for automotive application, the ignition system includes an individual coil that is associated with each spark plug of the engine. These individual coils are mounted on the upper end of the electrical terminal that connects the coil output to the spark plug. This presents a problem in servicing as may be best understood my reference to FIG. 1, which shows a typical prior art type of construction, utilized for this purpose.
As seen in this figure, an internal combustion engine, indicated generally by the reference numeral 21 has a cylinder head assembly, indicated generally by the reference numeral 22. This cylinder head assembly 22 is comprised of a cylinder head 23 and a cam cover 24 that is affixed to the cylinder head 23 with a sealing gasket interposed there between (not shown). This defines a cam chamber 25 in which a valve actuating mechanism, shown partially and identified by the reference numeral 26 is positioned.
The cylinder head 23 has a lower surface in which combustion chamber recesses 27 are formed. The combustion chamber recesses 27 of the cylinder head defining the combustion chamber is formed with a tapped opening 28 so as to receive the threaded end of a spark plug 29 with its terminals projecting into the combustion chamber.
It will be seen that the upper end of the spark plug 29 extends into a tubular spark plug tube 31 which has its lower end sealingly engaged in a spark plug tube receiving pocket 32 of cylindrical configuration formed in a lower surface 33 of the cylinder head 23. This tubular spark plug tube 31 extends upwardly and passes through an opening 34 formed in the cam cover 24 with a sealing grommet 35 being interposed there between.
The spark plug is fired by a coil 36 that is activated by an associated ignition system and terminal 37 that are inserted into the tubular spark plug tube 31 with the lower end of the terminal engaged with the terminal end of the spark plug 29 as shown in the cylinder to the right in FIG. 1.
A problem in connection with servicing arises, however, when the placement of the engine 21 is such that one or more of the tubular spark plug tube 31 is disposed in an obstructed area. For example, FIG. 1 shows a conventional brake booster 38, which overlies the end cylinder of the engine and accordingly blocks the removal of the coil 36 and terminal 37 for servicing of the spark plug 29.
In addition to the servicing problem, this type of construction also presents difficulty in engine assembly. That is, it is necessary when building the engine or when servicing the engine to place all of the tubular spark plug tube 31 in the cylinder head 23 and then attach the cam cover 24 while guiding the sealing grommets 35 around the periphery of the upwardly projecting tubular spark plug tube 31. The greater number of cylinders, the more difficult it is to connect and assemble them.
It is, therefore, a principal object to this invention to provide an improved cylinder head structure of this general type, but one in which the spark plugs can be easily accessed for servicing without encountering the problems in connection with the prior art type of construction.
It is a further object to this invention to provide an improved spark plug receiving tube assembly for the cylinder head of an internal combustion engine that facilitates servicing and minimizes operational and assembly costs.
This invention is adapted to be embodied in a cylinder head assembly for an internal combustion engine that comprises a cylinder head and a cam cover. The cam cover is affixed to the cylinder head so as to define a cam chamber between an upper surface of the cylinder head and the interior of the cam cover. The cylinder head is formed with at least one spark plug receiving, threaded hole leading into a combustion chamber of the cylinder head. The cylinder head forms a spark plug tube attaching hole that is greater in diameter than and surrounds the at least one spark plug receiving, threaded hole. A spark plug tube inserting hole is formed in the cam cover and is aligned with the cylinder head spark plug tube attaching hole. A lower spark plug tube is sealingly affixed at one end thereof to the cylinder head spark plug tube attaching hole. An upper spark plug tube is sealing engaged at one end thereof to the cam cover spark plug tube attaching hole and is sealingly engaged at the other end thereof to the other end of the lower spark plug tube.